Umbilical Cord Blood (UCB)-derived stem cells, which are non-embryonic, are non-controversial (with approval by the Vatican and all religious groups), and offer the potential for numerous “off the shelf” cell therapeutic products that are easier to obtain and faster to distribute than individual adult directly donated bone marrow and blood cells. An emerging technology, UCB stem cell grafts for treatment of hematology patients have a U.S. market potential of $425 million/year, with additional market potential combining Europe, Asia, and S. America of $978 million/year, rendering a world-wide market potential of $1.4 billion annually and growing. Cord blood not only has these immediate therapeutic applications in hematology patients, but many more in the pipeline in regenerative medicine applications. So far, doctors have found the most promise in cord blood for conditions such as blood cancers, leukemia, and sickle-cell anemia. In addition, UCB, like embryonic stem cells, contains multi-potential stem cells that give rise to all somatic cells. Many investigators believe that UCB will eventually prove useful in regenerative medicine, helping patients with cardiovascular disease, spinal bifida, traumatic brain injuries, and neurodegenerative disorders. However, successful infusion and engraftment in humans of CD34+ hematopoietic stem cells (HSC) from a UCB graft is challenged by the cellular content that is generally a log order less in total cell dose than that of bone marrow or mobilized peripheral cells from adult donors.
Hematopoietic stem cells are multipotent stem cells that give rise to all the blood cell types including human CD34+ stem cell. The CD34 molecule is a cluster of differentiation molecules present on certain cells within the human body. It is a cell surface glycoprotein and functions as a cell-cell adhesion factor. It may also mediate the attachment of stem cells to bone marrow extracellular matrix or directly to stromal cells. CD34 is also the name for the human gene that encodes the protein.
Cells expressing CD34 (CD34+ cell) are normally found in the umbilical cord and bone marrow as hematopoietic cells and tend to migrate from the blood stream to the bone marrow along a gradient of stromal derived factor-1 (SDF-1) where SDF-1 levels are high in the bone marrow and low in the peripheral blood. SDF-1 is a cytokine belonging to the chemokine family CXCL12. When a bone marrow transplant patient receives allogeneic UCB mononuclear cells via intravenous infusion, successful engraftment entails UCB stem cells taking up residence in the patient's bone marrow. A peripheral blood mononuclear cell is any blood cell having a round nucleus. Activation of the complement system in the transplant patient as part of the stress response elicited by chemoradiotherapy conditioning activates proteases in the marrow that reduce SDF-1 concentration. Low SDF-1 levels in the bone marrow tend to lessen homing and engraftment of allogeneic UCB CD34 stem cells. Because the numbers of CD34+ hematopoietic stem cells (HSC) in UCB is low, methods to enhance engraftment of this population of cells are needed.
Since the first unrelated donor UCB transplant in 1993 it has been demonstrated that cryopreserved UCB from HLA 0-2 antigen mismatched unrelated donors contain sufficient numbers of transplantable hematopoietic stem and progenitor cells or reliable engraftment in most recipients weighing <40 kilograms (kg) and that it is associated with a low incidence of acute graft-versus-host disease (GVHD) despite substantial disparities in HLA between the donor and recipient. Yet, poor engraftment and slow rate of neutrophil and platelet recovery remain important challenges that increase risk of transplant-related mortality (TRM).
The ‘double’ UCB transplant (UCBT) platform was initiated as a potential strategy for testing graft manipulations and h its safety and efficacy has been established. In addition, we and others have shown that its utility as a model for testing of novel strategies in which one unit manipulated and the second is left unmanipulated to maximize safety. This strategy offers the additional advantage of being able to ‘track’ the manipulated unit's lympho-hematopoietic progeny over time based on the inherent genetic differences between the two UCB units and the recipient. Importantly, the double UCBT approach has transformed the field by extending the eligibility of transplantation to nearly all patients regardless of size and racial or ethnic background.
Engraftment is the single most important barrier to successful use of UCB. In comparison to mobilized peripheral blood and marrow from adult unrelated donors, time to neutrophil recovery and ultimate engraftment after UCBT is markedly delayed. Engraftment of HSC and hematopoietic progenitors after transplantation is the result of a complex series of events within the marrow microenvironment, involving adhesion and migration, integrity of the ‘stem cell niche and presence of chemotactic cytokines and growth factors that either preserve ‘sternness’, prevent or promote apoptosis or incite lineage-specific expansion and differentiation. While it is clear that UCB HSC have the capacity to engraft and insure life-long hematopoietic reconstitution (>20 years in the longest surviving UCBT recipient), interest in ex vivo expansion of HSC and progenitors has largely been driven by the clear association between cell dose and time to hematopoietic recovery and incidence of engraftment. Delayed engraftment may also be the result of the higher proportion of UCB CD34 in G0 and greater likelihood of HLA mismatch.
Limitations of current management of vascular disease include re-occlusion and diffuse small vessel disease. Prior evidence links the level of circulating marrow-derived HSC, characterized by expression of CD133 and CD34, with the occurrence of ischemic vascular events. HSC which express CD34 and CD133 surface markers have been shown in models of acute and chronic ischemia to augment blood flow and prevent myocardial necrosis There is emerging evidence of age-related diminution in the number and function of marrow-derived CD34/133+ HSC in response to ischemia.
There is a long felt need in the art for compositions and methods to increase engraftment of UCB stem and T-cells, as well as other sources of stem and hemopoietic stem and progenitor cells. The present invention satisfies these needs.